Electric sewing machine



2 Sheets-Sheet 1 Filed April 29, 1964 INVENTOR l/EL AZQUEZ JAME5 A.

July 4, 1967 J. A. VELAZQUEZ ELECTRIC SEWING MACHINE 2 Sheets-Sheet Filed April 29, 1964 INVENTOR. JAMES A. VELA mufiz ATTOEWEX employed to synchronize the underthread United States Patent 3,329,114 ELECTRIC SEWING MACHDIE James A. Velazquez, 65 Grove Ave., Cedarhurst, N.Y. 11516 Filed Apr. 29, 1964, Ser. No. 363,424 7 Claims. (Cl. 112-220) This invention relates to sewing machines and more particularly to improved means for reciprocably moving the needle through the fabric.

Much of the high speed sewing machine art is devoted to means for vertically reciprocating a thread-bearing needle through a fabric workpiece. Complex cams, gears, linkages, etc., are required to impart any substantial degree of usable energy to a needle having no appreciable mass and therefore very little inertia. Both industrial and home use sewing machines are quite expensive owing to the fact that the components needed to drive the needle at high speed are themselves driven at high speed. The

cams, gearing, bearings, shafts, etc., of the prior art machines must be fabricated to extremely close tolerances. This results in high product costs as well as a relatively delicate piece of machinery that is subject to excessive wear and repair.

The present invention is directed, in part, towards novel needle reciprocating means. Whereas, the prior art teaches the application of needles that are movable with respect to the means that hold them, the present invention contemplates using a needle that is rigidly secured to a cantilevered arm, the arm being arcuately pivotable at a point remote from the needle. A single power source is provided with a plurality of driving gears which reciprocate the needle bearing end of the arm in a substantially vertical plane.

In the present invention all need for camming is eliminated and only one crank arm is required to synchronize the underthread supply spool with the needle movement. An adjustably positioned hooker mechanism cooperates with the needle and supply spool to apply proper tension to the thread after it passes through the fabric workpiece.

Accordingly, it is an object of this invention to provide a low cost sewing machine characterized by a substantial reduction in the number of parts required.

It is another object to provide an improved high speed sewing machine wherein the needle is fixed in a reciprocating arm.

A further object is to provide simplified drive means for the aforementioned reciprocating, needle-bearing arm. It is an additional object to provide a sewing machine having a cantilevered needle-bearing arm arcuately reciprocated by the linear motion of a solenoid core.

These and other features, objects and advantages of the invention will, in part, be pointed out with particularity and will, in part, become obvious from the following more detailed description of the invention, taken in conjunction with the accompanying drawing, which forms an integral part thereof.

In the various figures of the drawing, like reference characters designate like parts.

In the drawing:

FIG. 1 is a fragmentary side elevation of the present invention with parts broken away to illustrate certain operating mechanism;

FIG. 1A schematically illustrates the crank arm motion supply spool and the needle movement.

FIG. 2 is a partial plan view taken along line 2-2 of FIG. 1;

FIG. 3 is a sectional view through the underthread spool trough taken along line 3-3 of FIG. 1;

FIG. 4 is a transverse sectional 4-4 of FIG. 3;

FIG. 5 is an exploded view of the underthread supply spool;

FIG. 6 is an end view of the underthread supply spool assembly taken along line 6-6 of FIG. 5; and

FIGS. 7A, 7B and 7C schematically illustrate the formation of the loop in relation to various angular displacements of the hooker assembly.

There is schematically shown a sewing machine 10 comprised, in part, of base member 12 and arm 14. The head end 16 of arm 14 contains a sewing needle 18 rigidly secured thereto by means of set screw 20. Presser foot 22 is also mounted in head end 16 in a resilient manner, the biasing being accomplished by compression spring 24. Head end 16 is provided with a stud 25 having a rotatable slotted head 27. The undercut slot is adapted to accommodate and retain the length of thread as it passes from the upper thread spool supply to the needle. As head end 16 is lowered and raised with respect to the presser foot, the slack in the upper thread is increased and decreased. This action tends to facilitate the passage of the upper thread loop about the leading end of the underthread as will be explained more fully hereinafter.

At its rearward end 26, arm 14 is pivotally mounted on transverse shaft 28 which is rotatably journaled in outboard support blocks 30 secured to base member 12. Rigidly secured to shaft 28, for rotation therewith, is a sector gear 32. Tab 34 provides means to anchor the gear to the arm through pin 36 so that any arcuate movement of the sector gear will be reflected in a similar motion of the entire arm including the needle.

Sector gear 32 is in meshing engagement with a drive pinion 38 which is rotatably journaled in clevis arm 40. Screws 42 secure the clevis arm to the top surface of base member 12. Solenoid S, disposed in base member 12 has gear mounting bracket 44 secured to its linearly movable core. It will be seen in FIG. 1 and FIG. 2 that rack gears 46, 48, 5t and 52 are mounted in bracket 44. Legs 44a and 44b are in the form of channels spaced on either side of the longitudinal axis of pinion 38. When the solenoid is energized, the core will move upwardly, carrying with it bracket 44 and the set of gears 46, 48, 50 and 52. Gear 46 will first come into meshing engagement with pinion 38 causing the pinion to be rotated counterclockwise. Sector gear 32 will thereby be rotated clockwise, as will arm 14, and this motion will enable thread-carrying needle 18 to pierce the fabric workpiece.

Further upward motion of the solenoid core will cause gear 46 to move past pinion 38 and will bring the next successively lower gear 48 into meshing engagement with pinion 38. Proper dimension of gear location will exactly determine the length of engagement of successive gears in order to eliminate any time lag. To accomplish this, the gears may be adjustably mounted in bracket 44. Since gear 48 is positioned on the side of pinion 38 opposite to gear 46, gear 48 will cause pinion 38- to rotate now in a clockwise direction and therefore sector gear 32 will rotate in a counterclockwise direction. Arm 14, secured to the sector gear through pin 36, will thereby be raised, taking the needle out of the fabric workpiece. The same pattern will be imparted to the arm and the needle as the core continues upwardly to bring the next two gears 50 and 52 into successive meshing engagement with pinion 38. When the solenoid core reaches the end of its upward stroke and starts to move downwardly, alternate up and down motion will again be imparted to the needle. Thus it will be seen that for each complete cycle of the solenoid core, that is, one up stroke and one down stroke, the needle will make four complete stitches.

view taken along line While two pairs of solenoid driven gears have been illustrated, it should be understood that one or more pairs may be employed, the only practical limitation on the number of pairs being the size of the housing. The number of needle strokes per solenoid stroke will be a multiple of the number of pairs of gears used.

The solenoid is energized from a conventional 60 -cycle power source 53 and is controlled by switch 54. With the switch in the on position, current will flow through leads 56a and 56b and contacts 58a and 58b, respectively. The solenoid core will then be drawn upwardly, working against compression spring 60 and contacts 58a and 581) will open. As shown in FIG. 1 contact 58a is carried by bracket 58c for movement together with the solenoid core. The drawing illustrates the moment just prior to the upward movement of the solenoid core and the opening of the contacts. The solenoid core is urged downwardly by the spring to reclose the contacts so that the cycle is repetitive and continuous as long as switch 54 is closed or in the on position. Contact 58a may be in the form of a screw to provide a measure of adjustability to the contact spacing.

Still another gear 62 is mounted in the housing on transverse shaft 64. This gear is also in meshing engagement with sector gear 312 in order to synchronize the needle motion with the underthread supply spool and the hooker mechanism now to be described.

Ledge 66, integral with base member 12, is provided with a pair of spaced upright support posts 68 for rotatably journaling transverse shaft 6-1. Also carried by shaft 64 is a drive disc 70 having an eccentric crank arm 72 pivotally fixed thereto. By means of the eccentric crank arm, the oscillatory motion of the sector gear is converted to a rotary motion which drives the underthread supply spool and the hooker mechanism. A telescoping support member 74 is secured to the underside of the base member top surface and is pivotally connected to sleeve 76 slidably positioned on the crank arm intermediate the drive disc 7 and hooker assembly 78.

FIG. 1A schematically illustrates the crank arm act-ion. When arm 72 is at position A, pin 82 will be slightly off the theoretical center line xx at position B. When arm 72 is moved to position A by the gearing arrange-- ment, pin 82 will be moved to position B which is also off center line x-x. Thus it will be seen that as arm 72 is oscillated between points A and A, pin 82 will be rotated about nut 99 and will successively pass through points B and B.

End plate 80 of the hooker assembly is rotatably driven by the forward end of crank arm 72 through eccentrically mounted pin 82. The end plate is pinned or otherwise secured to shaft 84 which is journaled in one end wall of spool trough 86. It may best be seen in FIG. 3 and FIG. 4 that the spool trough 86 is fixed underneath the top surface of base member 12 and that end plate 80' will rotate about a fixed transverse axis. Cap 88 also secures the end plate to shaft 84 by means of nut 99 threaded onto the end of the shaft. The cap is also provided with an aperture 88a diametrically aligned with aperture 80a in the end plate to accommodate eccentric pin 82. Thus it will be seen that cap 88 and end plate 80 are driven as a single unit.

FIG. 3 and FIG. 4 illustrate a simple direction control assembly that permits shaft 84 to rotate only in one direction, that is, in the angular direction established by the motion of the crank arm. Manually adjustable ratchet wheel 90 is fixed to shaft 84 and pawl 92 is pivotally fixed to the end wall of spool trough 86 such that it is in engagement with the teeth of ratchet 90. The pawl will slip over the teeth when the ratchet is driven counterclockwise (FIG. 4) but will be locked into the teeth by the urging of spring member 94 to prevent :a clockwise rotation, as viewed in FIG. 4.

An underthread hooker and loop spreader, generally denoted by the reference character 100, is secured at the innermost end of shaft 84 for rotation therewith. The hooker body portion 102 is initially in a plane perpendicular to the longitudinal axis of shaft 84 and spool trough 86. However, a twist is given to the hooker body so that at a point proximate the top of the spool trough, the span of the hooker is parallel to the longitudinal axis of shaft 84 and trough 86. The hooker body is then provided with an arcu-ate portion 104 that is only slightly smaller than the inside diameter of the spool trough. It will be seen in FIG. 3 that the hooker is also provided with opposed transverse arms 106 and 108 as well as a central pointed portion 110.

To assure proper timing, the angular position of the hooker is adjustable by means of nut 99. Since the hooker is fixed to shaft 84, rotation of the nut will angula'rly change the position of central, pointed portion 110. Therefore the starting point of the crank mechanism will be changed since cap 88, end plate 80 and shaft 84 are a single unit driven through pin 82.

FIGS. 7A, 7B and 7C schematically illustrate the operation of the hooker mechanism. For clarity, only the hooker 100 and the underthread supply spool are shown. When the needle is forced downwardly through the fabric workpiece, it carries with it a loop of the upper thread. When the needle is pulled out of the fabric, it leaves the loop behind. The rotating hooker is suitably timed, as explained hereinabove, so that loop-engaging point 110 reaches the top of its arc just after the needle starts its upward travel with the upper thread loop left behind. Point 110 then engages the loop and starts to carry it about the outer diameter of the 'underthread supply source B.

As the hooker continues its arcuate travel about underthread supply source B, the slack is taken up in the loop and leg L of the loop slips down along arm 106 of the hooker, This will occur approximately when the hooker is at the lowermost point and is passing beneath supply source B. Leg L is therefore passed over the end of sup ply source B and as the hooker starts its upward, arcuate travel about the far side of supply source B, leg L will start to slip along arm 108. Before the hooker completes 360 of rotation, leg L of loop L will have passed over the opposite end of supply source B so that legs L and L straddle the upwardly extending length of thread T emanating from underthread supply source B.

It should be pointed out now that the underthre-ad supply source B, in order to accommodate the passage of legs L and L therebeneath, is of smaller diameter than the inside of spool trough 86. The construction of the trough, as illustrated, also permits the use of a conventional wooden spool of thread, as may be readily purchased at any notion store. With the present apparatus, it is not necessary to wind an underthread supply on a specially constructed bobbin. The trough is secured to the underside of base member 12 by means of an integral leg 87 and screws 89. Lip 91 is also formed on trough 86 so that the spool B may be conveniently dropped into place through hinged door 93 formed in the top surface of the base member. For this purpose, trough 86 is open on top with lip 91 extending inwardly towards and parallel to the longitudinal axis of the trough. Lip 91 is somewhat resilient so that the spool may be gently pushed into the trough but the spool is restrained from coming out when it is lifted upwardly by the passage of the thread loop. The lowermost wall of trough 86 is notched out at 95 to facilitate the passage of hooker 100.

FIG. 5 and FIG. 6 illustrate thread-tensioning means for the underthread supply spool which is ordinarily made of wood and is provided with a central cylinder having a longitudinal bore and a pair of flanges, one at each end of the cylinder. Plug 122 is force-fit into the spool so that the small, radially extending, tapered riblike fins 124 bite into the longitudinal bore of the spool. A metallic washer 126 is then slipped over shank portion 128 and this is followed by an idler pulley 130- and .a

hits stop felt washer 134. Nut 1'36 threadably engages the end of plug 122 so that in effect, the shank of the nut is an extension of the plug shank. The two washers and the pulley are thereby rotatably secured proximate one end of supply source B.

A length of thread T is unwound from the supply source and wrapped several times around the groove of pulley 130. A pair of flexible guard members 138a and 13811 are then snapped onto the periphery of the spool. Suitable. grooves are provided in the end faces of the pulley for this purpose. The thread is then led longitudinally past the spool body and through resilient guide means 140. Spring finger 142 is provided so that the guide means maybe snapped into the longitudinal bore of the spool rat the end thereof opposite plug 122. The guide means is further provided with a pair of resilient, concentrically mounted rings 144 and 146. The thread is passed between rings 144 and 146 before extending upwardly where it is locked by the loop, as explained hereinabove. A certain amount of drag is imparted to the thread by wrapping it :around the pulley so that the tension thereon is uniform and predictable. The tension may be increased or decreased simply by tightening or loosening nut 136 and bringing washer 134 into more or less frictional engagement with the side face of pulley 130.

Referring once again to FIG. 1, it will be seen that the upper thread supply spool is rotatably mounted on standoff 150 .which is threadably secured to vertical post 151 mounted in the top surface of base member 12. A felt washer 152 which bears against one end of the spool is provided beneath the head of standoff 150 so that a certain amount of drag or braking maybe applied to the rotating spool merely by axially moving the threaded standoff. It is common in much of the prior art to hold the spool fixed against rotation and have the thread helically removed therefrom. With that arrangement, the tension on the thread was diflicult to predict and even tended to cause backlash in the upper thread. A length of thread is unwound from the spool and hooked around resilient finger 153 in order to provide additional drag. The thread is then led around pulley 154 which is rotatably supported in cutout 156 formed in the head end 16 of arm 14, before it is inserted in the eye of the needle.

FIG. 3 illustrates pulley 154 rotatably mounted on transverse shaft 160. A spring 158 is positioned about shaft 160 with the ends fixed to pulley 154 and shaft 160 so as to rotate the pulley 154 clockwise (when viewed from the right) until pin 159a, extending from pulley 154,

15%. Rotation of shaft 160 increases or decreases spring tension depending on the direction of rotation. Thus, when the thread is passed over the pulley, additional drag will be applied to the thread as determined by the setting of shaft 160.

The apparatus described hereinabove is relatively simple to manufacture at low cost. Many components that were absolutely essential to prior art devices have been eliminated. By simplifying the operating mechanism, the servicing or repairing thereof is also simplified.

The novel means to reduce the number of parts required includes holding the needle rigidly in an arcuately movable pivotal housing. By making the pivot point remote from the needle, a small motion at the pivot end will result in a relatively large moment of inertia at the needle-bearing end. A simple yet effective means for imparting arcuate motion is provided by a rack and pinion system which multiplies a single solenoid stroke into a plurality of needle strokes.

Direct coupling means connects the needle drive mechanism to means for hooking and spreading the loop left below the fabric workpiece by the needle. The hooker mechanism cooperates with an underthread supply spool that is nothing more than the conventional wooden spool of thread that may be purchased in any notions store. Therefore, a larger supply of underthread may be contained in the machine thus eliminating the need for the frequent winding of a specialized bobbin. Suitable tensioning and drag means have been provided for both the upper and lower threads.

There has been disclosed heretofore the best embodiments of the invention presently contemplated and it is to be understood that various changes and modifications may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. An electric sewing machine having upper and lower thread supplies and a thread carrying needle, said sewing machine comprising:

(A) a base member;

(B) an arm pivotally mounted at one end thereof in said base member, the opposite end of said arm rigidly securing the needle whereby the needle is arranged to move through a work piece in a substantially vertical plane when said arm is pivoted;

(C) drive means arranged to oscillate said arm in two angularly opposite directions about the pivot point of said arm, said drive means comprising:

(a) a gear member rotatably journaled in said base member, said gear member being rigidly secured to said arm whereby angular movement of said gear produces a like angular movement of said arm;

(b) a pinion in meshing engagement with said gear member;

(c) a plurality of rack gears disposed on either side of the rotational axis of said pinion, said rack gears being in alternately staggered relationship with each other whereby said rack gears are adapted to be placed in successive meshing engagement with said pinion; and

((1) means to linearly displace said rack gears into successive engagements with said pinion, each of said engagements resulting in a reversal of angular motion of said pinion, said gear member and said arm,

(D) coupling means responsive to the oscillatory motion of said arm, said coupling means having first and second ends, said coupling means first end being arranged for angular, bidirectional motion, said coupling means second end being arranged for a unidirectional rotary motion; and

(E) rotatable upper thread-engaging means connected to said coupling means second end whereby said thread-engaging means engages the upper thread carried by the needle and locks the upper thread about the lower thread to form a stitch.

2. An electric sewing machine having upper and lower thread supplies and a thread-carrying needle, said sewing machine comprising:

(A) a base member;

(B) an arm pivotally mounted at one end thereof in said base member, the opposite end of said arm rigidly securing the needle whereby the needle is arranged to move through a work piece in a substantially vertical plane when said arm is pivoted;

(C) drive means arranged to oscillate said arm in two angularly opposite directions about the pivot point of said arm;

(D) coupling means responsive to the oscillatory motion of said arm, said coupling means having first and second ends, said coupling means first end being arranged for angular, bidirectional motion, said coupling means second end being arranged for a unidirectional rotary motion; and

(E) rotatable upper thread-engaging means connected to said coupling means second end whereby said thread-engaging means engages the upper thread carried by the needle and locks the upper thread about the lower thread to form a stitch, said. upper thread engaging means further comprising:

(a) a disc rotatably driven by said coupling means second end;

(b) an upper thread loop hooker and spreader rotated by said disc, said loop hooker and spreader being arranged for rotation about the lower thread supply; and

(c) adjustment means adapted to vary the angular position of said loop hooker and spreader, said loop hooker and spreader comprising:

(1) a base portion secured to said adjustment means;

(2) an arcuate midsection disposed substantially at right angles to said base portion and substantially parallel to the longitudinal axis of the under thread supply, said midsection having a diametric dimension slightly larger than the under thread supply; and

(3) an upper thread engaging centrally pointed end having two opposed transverse arms of different lengths.

3. The apparatus of claim 2 wherein the shorter of the two transverse arms is rearward of said centrally pointed end and said second transverse arm is rearward of said first arm, the dimension between the ends of said arms being larger than the length of the underthread supply.

4. The apparatus of claim 2 wherein said adjustment means comprises:

(a) a threaded shaft secured to said disc and extending therethrough;

(b) a ratchet wheel secured to said shaft proximate said loop hooker and spreader;

(c) an underthread supply trough secured to said base member, said shaft being rotatable within said trough;

(d) a pawl member secured to said trough and in engagement with said ratchet wheel, said pawl permitting rotation of said ratchet wheel only in the same direction as said disc; and

(e) a nut secured to said shaft opposite said ratchet wheel whereby turning said nut will angularly displace said loop hooker and spreader.

5. An electric sewing machine having upper and lower thread supplies and a thread-carrying needle, said sewing machine comprising:

(A) a base member;

(B) an arm pivotally mounted at one end thereof in said base member, the opposite end of said arm rigidly securing the needle whereby the needle is arranged to move through a work piece in a substantially vertical plane when said arm is pivoted;

(C) drive means arranged to oscillate said arm in two angularly opposite directions about the pivot point of said arm;

(D) coupling means responsive to the oscillatory motion of said arm, said coupling means having first and second ends, said coupling means first end being connected to said drive means and arranged for angular, bidirectional motion, said coupling means second end being arranged for a unidirectional rotary motion;

(E) rotatable upper thread-engaging means connected to said coupling means second end whereby said thread-engaging means engages the upper thread carried by the needle and locks the upper thread about the lower thread to form a stitch;

(F) first and second upper thread tensioning means, said second upper thread tension means comprising:

(a) a pulley rotatably mounted in said arm proximate the needle whereby the upper thread rides on said pulley intermediate said first upper thread-tensioning means and the needle; and

(b) biasing means arranged to urge said pulley in an angular direction opposite to that of the linear travel of the upper thread; and

(G) lower thread tensioning means.

6. The apparatus in accordance with claim 5 including an axle threadably mounted in said arm, said pulley being loosely mounted on said axle and stop means arranged to limit the angular movement of said pulley.

7. The apparatus of claim 5 wherein said lower threadtensioning means comprises:

(a) a ribbed shaft mounted in the underthread supply at one end thereof;

(b) a grooved roller rotatably mounted on said shaft,

one face of said roller abutting against the underthread supply, the groove of said roller being in a plane perpendicular to the rotational axis of the underthread;

(c) a friction washer mounted on said shaft, said washer abutting the exposed face of said roller;

((1) means abutting said friction washer whereby the frictional force between said roller and the underthread supply source may be increased and decreased; and

(e) a pair of concentric resilient rings mounted in the underthread supply at the end thereof opposite said roller, said rings being arranged to receive a length of underthread therebetween.

References Cited UNITED STATES PATENTS 93,588 8/1869 Bond 1l2--l8l 2,250,939 7/1941 Winkley 11222l 2,932,266 4/1960 Lutz et a1 112169 X FOREIGN PATENTS 1,164,030 5/ 1958 France.

JORDAN FRANKLIN, Primary Examiner.

H. HUNTER, Assistant Examiner. 

1. AN ELECTRIC SEWING MACHINE HAVING UPPER AND LOWER THREAD SUPPLIES AND A THREAD CARRYING NEEDLE, SAID SEWING MACHINE COMPRISING: (A) A BASE MEMBER; (B) AN ARM PIVOTALLY MOUNTED AT ONE END THEREOF IN SAID BASE MEMBER, THE OPPOSITE END OF SAID ARM RIGIDLY SECURING THE NEEDLE WHEREBY THE NEEDLE IS ARRANGED TO MOVE THROUGH A WORK PIECE IN A SUBSTANTIALLY VERTICAL PLANE WHEN SAID ARM IS PIVOTED; (C) DRIVE MEANS ARRANGED TO OSCILLATE SAID ARM IN TWO ANGULARLY OPPOSITE DIRECTIONS ABOUT THE PIVOT POINT OF SAID ARM, SAID DRIVE MEANS COMPRISING: (A) A GEAR MEMBER ROTATABLY JOURNALED IN SAID BASE MEMBER, SAID GEAR MEMBER BEING RIGIDLY SECURED TO SAID ARM WHEREBY ANGULAR MOVEMENT OF SAID GEAR PRODUCES A LIKE ANGULAR MOVEMENT OF SAID ARM; (B) A PINION IN MESHING ENGAGEMENT WITH SAID GEAR MEMBER; (C) A PLURALITY OF RACK GEARS DISPOSED ON EITHER SIDE OF THE ROTATIONAL AXIS OF SAID PINION, SAID RACK GEARS BEING IN ALTERNATELY STAGGERED RELATIONSHIP WITH EACH OTHER WHEREBY SAID RACK GEARS ARE ADAPTED TO BE PLACED IN SUCCESSIVE MESHING ENGAGEMENT WITH SAID PINION; AND (D) MEANS TO LINEARLY DISPLACE SAID RACK GEARS INTO SUCCESSIVE ENGAGEMENTS WITH SAID PINION, EACH OF SAID ENGAGEMENTS RESULTING IN A REVERSAL OF ANGULAR MOTION OF SAID PINION, SAID GEAR MEMBER AND SAID ARM, (D) COUPLING MEANS RESPONSIVE TO THE OSCILLATORY MOTION OF SAID ARM, SAID COUPLING MEANS HAVING FIRST AND SECOND ENDS, SAID COUPLING MEANS FIRST END BEING ARRANGED FOR ANGULAR, BIDIRECTIONAL MOTION, SAID COUPLING MEANS SECOND END BEING ARRANGED FOR A UNIDIRECTIONAL ROTARY MOTION; AND (E) ROTATABLE UPPER THREAD-ENGAGING MEANS CONNECTED TO SAID COUPLING MEANS SECOND END WHEREBY SAID THREAD-ENGAGING MEANS ENGAGES THE UPPER THREAD CARRIED BY THE NEEDLE AND LOCKS THE UPPER THREAD ABOUT THE LOWER THREAD TO FORM A STITCH. 